Left ventricular band has been considered a vestigial entity for quite a long time. Their incidence is quite common in our day to day practise but their real function is yet to be understood. We performed a case series of 5 patients with left ventricular band and studied the characteristics of the band along with their hemodynamic effects. The study showed that the characteristics of the band depend on the degree of left ventricular outflow obstruction and varies among people of different age groups. The ventricular band also play a role in sequestration of blood in the left ventricle and they are also involved in maintaining the geometry of the left ventricle in diseased conditions.

Left ventricular fibromuscular bands, alternatively known as false tendons, are distinct fibromuscular filaments of varying length and thickness. The reported prevalence of the left ventricular false tendons (LVFTs) varies from 2% to 71% depending on the type of study. A male preponderance has been demonstrated.

LVFT contains conducting tissue which may be extensions of the bundle of his. They also contain connective tissue, especially in thin oyster white LVFT, and diffuse, scanty strands of myocardial cells. LVFT is either longitudinal or transverse in orientation. The longitudinal LVFT usually contain connective and conductive tissue. They become taut in diastole and loose and irregular in systole. Transverse LVFT is associated with hemodynamic effects of sequestration. They may be responsible for the features of early repolarization. Here, we describe a case series of five patients of varied age groups having transverse left ventricle (LV) band on echocardiography along with other associated abnormalities. The role played by LVFT in assisting ventricular function in various conditions has also been discussed.

Patients and Methods

This case series is a cross-sectional analysis of five patients who presented with varied complaints and their echocardiography revealed a transverse LV band along with other entities. The age group of the patients ranged from 50 days to 65 years. Consent was obtained either from the patients or from their guardians in case they were minors.

These patients were evaluated using transthoracic echocardiography done on a Wipro GE machine (VIVID T8) using a linear echocardiography probe of 3.5 MHz frequency. LV false tendons visible in at least 2 views were considered as definite. Routine measurements, using the conventional views, were taken. The characteristics of the LV bands were noted in terms of position, extent, point of insertion, end systolic, and end diastolic appearance. The effect of false tendons on LV hemodynamics was also evaluated. The left ventricular outflow tract (LVOT) gradient was estimated in each patient, and correlation was sought for between the gradient and the visual estimation of the thickness of the band. The severity of LVOT obstruction was graded as mild (mean pressure gradient [PG] <20 mm Hg), moderate (mean PG 20–40 mm Hg), and severe (mean PG >40 mm Hg). The dimensions of the LV band could not be evaluated as 3D Echo facilities are not available at our center. Transesophageal echocardiography (TEE) was not done.

Follow-up of these patients could not be done as the majority of them were evaluated as outpatients.

Results

In this case series, the youngest patient was a 50-day-old boy, and the oldest case was a 65-year-old male patient. Among the five cases, two patients were healthy and underwent echo for noncardiac indications whereas the rest had cardiac complaints. Echocardiography revealed the presence of a transverse fibrous cord like structure stretching across the LV cavity in all these patients. Among these five patients, two patients had a normal echo except for the LV band, two patients had bicuspid aortic valve, and one patient had degenerative tricuspid aortic valve disease.

In the healthy group, the LV band appeared robust and discrete, as the right ventricle (RV) moderator band, in a 10-year-old female whereas it was thin, apical and rudimentary in a 40-year-old male. The LVOT gradient was normal in both these patients [Figure 1] and [Figure 2]. In the bicuspid valve group, the first patient was a 50-day-old newborn boy whose echo showed a very thick robust LV band approximately the thickness of interventricular septum. The LV band extended from interventricular septum to the free wall, mimicking subvalvular membrane but differing from it in position [Figure 3]. The LVOT gradient in this patient revealed severe LVOT obstruction. The other patient, a 40-year-old male, had an LV band extending from the papillary muscle to the LV free wall. The thickness of the LV band was visibly less as compared to the 50 days newborn [Figure 4]. His LVOT gradient revealed moderate LVOT obstruction. The last patient was a 65-year-old man whose echo revealed a degenerative tricuspid aortic stenosis with an LV band which was distinct but not as robust and thick as those seen with bicuspid aortic valves. In systole, LVFT became loosened and irregular suggesting that there was no hypertrophy of myocardial cells [Figure 5].

LV band has been seen to play a role in LV hemodynamics. A robust LVFT, even in healthy individuals, sequestrates blood below the band and pushes it toward LVOT, a function akin to the moderator band of RV. It was seen that a certain amount of inlet flow was returned from the band toward the base even as the flow toward apex continued [Figure 6]. The extent of sequestration was further reflected by the presence of aliasing at the LV inlet as the sequestered blood tried to cross the inlet flow and move toward LVOT [Figure 7]. Confirmation of sequestration was done by placing a pulsed wave Doppler at inlet flow and the band. The tracing showed some retrograde flow suggestive of bidirectional flow [Figure 8].

Discrete fibromuscular bands in the LV cavity have been identified on morphological examination in 48% of subjects of all ages that included patients with congenital heart disease, acquired structural heart disease, and those with normal hearts.[1] The incidence of LVFT on echocardiography has been estimated to be 71% among 187 healthy adults in a prospective study performed by Suwa et al.[2] Other retrospective studies, however, showed a lower incidence. Orientation and dimension of LVFT vary both in health and disease. The orientation of LVFT is important as transverse bands are associated with more hemodynamic consequences as compared to longitudinal bands. LVFT is associated with early repolarization (as it contains conductive tissue within) and has been associated with idiopathic ventricular tachycardia.[3] Transverse relaxation of LV occurs more compared from longitudinal relaxation. Hence, the transverse band gets overstretched. These stretched myocardial cells repolarize early thereby creating a voltage gradient between endocardium and epicardium, resulting in elevated ST segment. It may also produce hemodynamic effects, as it contains myocardial cells, by sequestrating blood proximal to the band.

This case series was done for the purpose of evaluation of properties of LV band in healthy individuals and individuals with other associated abnormalities. It also sought to evaluate the hemodynamic effects of an LV band. Among the five cases studied, two were apparently healthy individuals.

In the case of the 10-year-old child who had no structural abnormality, we could demonstrate the thickness was similar to moderator band of RV. The band effectively sequestrated blood proximal to it. The retrograde flow thus generated was seen moving toward the LVOT crossing the mitral inlet flow producing some aliasing. It appears that with growing age if the heart has no structural abnormality and LV function is normal, the LV band regresses. Authentication will require serial echocardiography scanning over several decades. In normal healthy adults, we were able to demonstrate an LV band which was more apical and rudimentary, i.e., thinner than the moderator band of RV. No significant sequestration of blood proximal to the band was demonstrated. In patients with bicuspid aortic valve, we could demonstrate a robust LV band with sequestration evident in color flow. The LVOT gradient was considerably high in the newborn as compared to the other patient. The visible thickness of the LV band was different between the two patients, the LV band being very thick in the 50-day-old newborn and comparable to the RV moderator band. Thus it may be inferred that the thickness of the LV band is proportional to the severity of LVOT obstruction. In the patient with degenerative aortic valve stenosis, the LV band was loose and not as robust as the other patients. The shortening of LV band during systole was less as compared to other cases which might indicate the reduced number of myocardial contractile elements within the LV band. It could be possible that the number of contractile elements in the LV band decrease with time, and by the time of presentation of degenerative aortic stenosis, the band has become loose and has lost contractile function.

LV band is a quite common yet frequently ignored condition found in patients undergoing echocardiography for varied reasons. As its presence can be demonstrated in normal healthy individuals, its presence in diseased conditions may not be considered as of significant value. However, the LV band contains myocardial cells and akin to the moderator band of RV, stretches across the LV cavity. The difference in dimensions of the LV band found in patients with different conditions shows that there may be some relation between the characteristics of LV band and the underlying condition. There is also a considerable correlation between severity of LVOT obstruction and the LV band dimensions. The myocardial cells in the LV band may hypertrophy under conditions of increased wall stress and aid the function of the LV. The prevalence of LV band is more in patients with LV systolic dysfunction as shown in a study.[4] A study in patients with cardiomyopathy showed that the presence of LV bands was associated with lower prevalence of functional mitral regurgitation regardless of the cause of cardiomyopathy. This effect may be seen due to the effect of LV bands on the sub-valvular apparatus and its role in maintaining the LV geometry.[5] This needs to be validated by further studies.

The study of LV band is important to understand the effect of LV band on the process of ventricular remodeling and hemodynamics of the LV along with other clinical associations. The theory that the LV band is protective like the moderator band remains to be established and further large scale longitudinal studies are required in this matter.

Limitations

The number of cases studied was small. Hence, it is difficult to extrapolate the findings on the general population. This was a cross-sectional analysis and follow-up was not done. Therefore, changes in hemodynamics occurring over time could not be determined. The exact dimensions of the false tendon could not be determined as three-dimensional echo and TEE facilities were not available.